Distributed fiber optic sensors(DFOSs)possess the capability to measure strain and temperature variations over long distances,demonstrating outstanding potential for monitoring underground infrastructure.This study pr...Distributed fiber optic sensors(DFOSs)possess the capability to measure strain and temperature variations over long distances,demonstrating outstanding potential for monitoring underground infrastructure.This study presents a state-of-the-art review of the DFOS applications for monitoring and assessing the deformation behavior of typical tunnel infrastructure,including bored tunnels,conventional tunnels,as well as immersed and cut-and-cover tunnels.DFOS systems based on Brillouin and Rayleigh scattering principles are both considered.When implementing DFOS monitoring,the fiber optic cable can be primarily installed along transverse and longitudinal directions to(1)measure distributed strains by continuously adhering the fiber to the structure’s surface or embedding it in the lining,or(2)measure point displacements by spot-anchoring it on the lining surface.There are four critical aspects of DFOS monitoring,including proper selection of the sensing fiber,selection of the measuring principle for the specific application,design of an effective sensor layout,and establishment of robust field sensor instrumentation.These four issues are comprehensively discussed,and practical suggestions are provided for the implementation of DFOS in tunnel infrastructure monitoring.展开更多
Foam is utilized in enhanced oil recovery and CO_(2) sequestration.Surfactant-alternating-gas(SAG)is a preferred approach for placing foam into reservoirs,due to it enhances gas injection and minimizes corrosion in fa...Foam is utilized in enhanced oil recovery and CO_(2) sequestration.Surfactant-alternating-gas(SAG)is a preferred approach for placing foam into reservoirs,due to it enhances gas injection and minimizes corrosion in facilities.Our previous studies with similar permeability cores show that during SAG injection,several banks occupy the area near the well where fluid exhibits distinct behaviour.However,underground reservoirs are heterogeneous,often layered.It is crucial to understand the effect of permeability on fluid behaviour and injectivity in a SAG process.In this work,coreflood experiments are conducted in cores with permeabilities ranging from 16 to 2300 mD.We observe the same sequence of banks in cores with different permeabilities.However,the speed at which banks propagate and their overall mobility can vary depending on permeability.At higher permeabilities,the gas-dissolution bank and the forced-imbibition bank progress more rapidly during liquid injection.The total mobilities of both banks decrease with permeability.By utilizing a bank-propagation model,we scale up our experimental findings and compare them to results obtained using the Peaceman equation.Our findings reveal that the liquid injectivity in a SAG foam process is misestimated by conventional simulators based on the Peaceman equation.The lower the formation permeability,the greater the error.展开更多
Extracting gas from unconventional shale reservoirs with low permeability is challenging.To overcome this,hydraulic fracturing(HF)is employed.Despite enhancing shale gas production,HF has drawbacks like groundwater po...Extracting gas from unconventional shale reservoirs with low permeability is challenging.To overcome this,hydraulic fracturing(HF)is employed.Despite enhancing shale gas production,HF has drawbacks like groundwater pollution and induced earthquakes.Such issues highlight the need for ongoing exploration of novel shale gas extraction methods such as in situ heating through combustion or pyrolysis to mitigate operational and environmental concerns.In this study,thermally immature shales of contrasting organic richness from Rajmahal Basin of India were heated to different temperatures(pyrolysis at 350,500 and 650℃)to assess the temperature protocols necessary for hydrocarbon liberation and investigate the evolution of pore structural facets with implications for CO_(2) sequestration in underground thermally treated shale horizons.Our results from low-pressure N_(2) adsorption reveal reduced adsorption capacity in the shale splits treated at 350 and 500 C,which can be attributed to structural reworking of the organic matter within the samples leading to formation of complex pore structures that limits the access of nitrogen at low experimental temperatures.Consequently,for both the studied samples BET SSA decreased by~58%and 72%at 350℃,and~67%and 68%at 500℃,whereas average pore diameter increased by~45%and 91%at 350℃,and~100%and 94%at 500℃ compared to their untreated counterparts.CO_(2) adsorption results,unlike N_(2),revealed a pronounced rise in micropore properties(surface area and volume)at 500 and 650℃(~30%-35%and~41%63%,respectively for both samples),contradicting the N_(2) adsorption outcomes.Scanning electron microscope(SEM)images complemented the findings,showing pore structures evolving from microcracks to collapsed pores with increasing thermal treatment.Analysis of the SEM images of both samples revealed a notable increase in average pore width(short axis):by~4 and 10 times at 350℃,~5 and 12 times at 500℃,and~10 and 28 times at 650℃ compared to the untreated samples.Rock-Eval analysis demonstrated the liberation of almost all pyrolyzable kerogen components in the shales heated to 650℃.Additionally,the maximum micropore capacity,identified from CO_(2) gas adsorption analysis,indicated 650℃ as the ideal temperature for in situ conversion and CO_(2) sequestration.Nevertheless,project viability hinges on assessing other relevant aspects of shale gas development such as geomechanical stability and supercritical CO_(2) interactions in addition to thermal treatment.展开更多
Since the Cenozoic,a series of extensional south-north normal faults and gneiss-granite domes evolved in the southern Tibetan Plateau,the formation mechanism of which is of scientific interest and which has implicatio...Since the Cenozoic,a series of extensional south-north normal faults and gneiss-granite domes evolved in the southern Tibetan Plateau,the formation mechanism of which is of scientific interest and which has implications for the tectonic dynamics of the plateau.Typical of such features are the Xainza-Dinggye rift and the Mabja gneiss dome,which are located in the Xainza-Xietongmen-Dinggye region in the central Tibetan Plateau.In this study,Magnetotelluric measurements across this region are used to generate a high-resolution 3-D electrical resistivity model of the subsurface and to analyze the cause of the conductive zones.The large-scale conductive zones identified in the middle-lower crust may result from aqueous melt partial melting,whereas the smaller-scale conductive zones in the upper-middle crust may result from saline fluids,possibly with varying minor volumes of melts.Subsequently,based on the electrical resistivity model and combined with the spatiotemporal coupling of the geological,geochemical,and geophysical data,the state and migration features of crustal materials are discussed.The results show that the upwelling of mantle materials along subduction channels and slab-windows related to the tearing of the Indian lithospheric plate contributed to the partial melting of the middle-lower crust in the Lhasa terrane.Furthermore,partial melting of the upper-middle crust in the Tethys-Himalaya terrane resulted from southern extrusion of crustal materials in the Lhasa terrane.These two mechanisms can significantly reduce the effective viscosity.We speculate that the deformation of the brittle upper crust that is controlled by large-scale ductile layers characterized by weak rheology is the main dynamic mechanism of rift evolution.Meanwhile,the metamorphism and anatexis in the upper-middle crust of the Tethys-Himalaya terrane related to the southern extrusion of materials contributed to the evolution of the Mabja gneiss dome.During the middle Miocene,the southern extrusion of crustal materials may have been influenced by the cooling events beneath the Mabja gneiss dome,which can explain why the deep areas beneath the Mabja gneiss dome have middle-high resistivity.In addition,our study region is located in the Mediterranean-Himalayan seismic belt,and mainly includes shallow-focus earthquakes and intermediate-depth earthquakes.In the north,shallow-focus earthquakes are mainly controlled by the accumulation of stress in the brittle layer of the overlying crust related to the ductile layer of the middle and lower crust.In the south,shallow-focus earthquakes(e.g.,Dingri MS6.8 earthquake)mainly occur in the rigid,resistive block,which is surrounded by conductive zones,possibly because fluid migration may be hindered by these resistive blocks.The intermediate-depth earthquakes are mainly controlled by the response in the subsurface area,which is related to the detachment of the Indian lithospheric mantle from the Indian crust.展开更多
Fracture network connectivity and aperture （or conductivity） distribution are two crucial features controlling flow behavior of naturally fractured reservoirs. The effect of connectivity on flow properties is well d...Fracture network connectivity and aperture （or conductivity） distribution are two crucial features controlling flow behavior of naturally fractured reservoirs. The effect of connectivity on flow properties is well documented. In this paper, however, we focus here on the influence of fracture aperture distribution. We model a two dimensional fractured reservoir in which the matrix is impermeable and the fractures are well connected. The fractures obey a power-law length distribution, as observed in natural fracture networks. For the aperture distribution, since the information from subsurface fracture networks is limited, we test a number of cases： log-normal distributions （from narrow to broad）, power-law distributions （from narrow to broad）, and one case where the aperture is pro- portional to the fracture length. We find that even a well- connected fracture network can behave like a much sparser network when the aperture distribution is broad enough （c~ 〈 2 for power-law aperture distributions and σ ≥ 0.4 for log-normal aperture distributions）. Specifically, most fractures can be eliminated leaving the remaining dominant sub-network with 90% of the permeability of the original fracture network. We determine how broad the aperture distribution must be to approach this behavior and the dependence of the dominant sub-network on the parameters of the aperture distribution. We also explore whether one can identify the dominant sub-network without doing flow calculations.展开更多
Wettability alteration of carbonate reservoirs from oil-wet to water-wet is an important method to increase the efficiency of oil recovery. Interaction between surfactants and polymers can enhance the effectiveness of...Wettability alteration of carbonate reservoirs from oil-wet to water-wet is an important method to increase the efficiency of oil recovery. Interaction between surfactants and polymers can enhance the effectiveness of surfactants in EOR applications. In this study, the interaction of polyethylene glycol(PEG) with an ionic surfactant, sodium dodecyl sulphate(SDS),is evaluated on an oil-wet carbonate rock surface by using contact angle measurements. The results reveal that wettability alteration of carbonate rocks is achieved through PEG/SDS interaction on the rock surface above a critical aggregation concentration(CAC). The behaviour of PEG/SDS aqueous solutions is evaluated using surface and interfacial tension measurements. Furthermore, the effect of PEG and SDS concentrations and impact of electrolyte addition on PEG/SDS interaction are investigated. It is shown that electrolyte(NaCl) can effectively decrease the CAC values and accordingly initiate the wettability alteration of rocks. Moreover, in a constant SDS concentration, the addition of NaCl leads to a reduction in the contact angle, which can also be obtained by increasing the aging time, temperature and pre-adsorption of PEG on the rock surface.展开更多
Quasi-rectangular shield tunneling is a cutting-edge trenchless method for constructing metro tunnels with double tubes,owing to its advantages in saving underground space and reducing ground disturbance.However,the c...Quasi-rectangular shield tunneling is a cutting-edge trenchless method for constructing metro tunnels with double tubes,owing to its advantages in saving underground space and reducing ground disturbance.However,the conventional quasi-rectangular shield tunneling method is not applicable when constructing a tunnel without a center pillar,such as a scissor crossover section of a metro line.Therefore,the O-0 tunneling method,which combines the quasirectangular shield and pipe jacking methods,was investigated in this study to solve the aforementioned construction challenges.This study presents a case study of the Sijiqing Station of the Hangzhou Metro Line 9 in China,in which the O-0 method was first proposed and applied.Key techniques such as switching between two types of tunneling modes and the tunneling process control in complex construction environments were investigated.The results demonstrated that the O-0 method can address the technical challenges presented by the post-transition line with a high curvature and a scissors crossover line.In addition,the adoption of the 0-0 method ensured that the transformation between shield tunneling and pipe jacking was safe and efficient.The ground settlement monitoring results demonstrated that the disturbance to the surrounding environment can be limited to a safe level.This case study contributes to the construction technology for a metro tunnel containing both post-transition lines with a small turning radius and a scissors crossover line.A practical construction experience and theoretical guidance were provided in this study,which are of significance for both the industry and academia.展开更多
基金funding support from Rijkswaterstaat,the Netherlands,and European Union’s Horizon 2020 Research and Innovation Programme(Project SAFE-10-T under Grant No.723254)China Scholarship Council,and National Natural Science Foundation of China(Grant No.42225702).
文摘Distributed fiber optic sensors(DFOSs)possess the capability to measure strain and temperature variations over long distances,demonstrating outstanding potential for monitoring underground infrastructure.This study presents a state-of-the-art review of the DFOS applications for monitoring and assessing the deformation behavior of typical tunnel infrastructure,including bored tunnels,conventional tunnels,as well as immersed and cut-and-cover tunnels.DFOS systems based on Brillouin and Rayleigh scattering principles are both considered.When implementing DFOS monitoring,the fiber optic cable can be primarily installed along transverse and longitudinal directions to(1)measure distributed strains by continuously adhering the fiber to the structure’s surface or embedding it in the lining,or(2)measure point displacements by spot-anchoring it on the lining surface.There are four critical aspects of DFOS monitoring,including proper selection of the sensing fiber,selection of the measuring principle for the specific application,design of an effective sensor layout,and establishment of robust field sensor instrumentation.These four issues are comprehensively discussed,and practical suggestions are provided for the implementation of DFOS in tunnel infrastructure monitoring.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.U2240210,52279098)the Natural Science Foundation of Jiangsu Province(Grant No.BK20200525)the Fundamental Research Funds for the Central Universities(Grant No.B230201021).We express our gratitude to PETRONAS and Shell Global Solution International B.V.for their support of this work.
文摘Foam is utilized in enhanced oil recovery and CO_(2) sequestration.Surfactant-alternating-gas(SAG)is a preferred approach for placing foam into reservoirs,due to it enhances gas injection and minimizes corrosion in facilities.Our previous studies with similar permeability cores show that during SAG injection,several banks occupy the area near the well where fluid exhibits distinct behaviour.However,underground reservoirs are heterogeneous,often layered.It is crucial to understand the effect of permeability on fluid behaviour and injectivity in a SAG process.In this work,coreflood experiments are conducted in cores with permeabilities ranging from 16 to 2300 mD.We observe the same sequence of banks in cores with different permeabilities.However,the speed at which banks propagate and their overall mobility can vary depending on permeability.At higher permeabilities,the gas-dissolution bank and the forced-imbibition bank progress more rapidly during liquid injection.The total mobilities of both banks decrease with permeability.By utilizing a bank-propagation model,we scale up our experimental findings and compare them to results obtained using the Peaceman equation.Our findings reveal that the liquid injectivity in a SAG foam process is misestimated by conventional simulators based on the Peaceman equation.The lower the formation permeability,the greater the error.
文摘Extracting gas from unconventional shale reservoirs with low permeability is challenging.To overcome this,hydraulic fracturing(HF)is employed.Despite enhancing shale gas production,HF has drawbacks like groundwater pollution and induced earthquakes.Such issues highlight the need for ongoing exploration of novel shale gas extraction methods such as in situ heating through combustion or pyrolysis to mitigate operational and environmental concerns.In this study,thermally immature shales of contrasting organic richness from Rajmahal Basin of India were heated to different temperatures(pyrolysis at 350,500 and 650℃)to assess the temperature protocols necessary for hydrocarbon liberation and investigate the evolution of pore structural facets with implications for CO_(2) sequestration in underground thermally treated shale horizons.Our results from low-pressure N_(2) adsorption reveal reduced adsorption capacity in the shale splits treated at 350 and 500 C,which can be attributed to structural reworking of the organic matter within the samples leading to formation of complex pore structures that limits the access of nitrogen at low experimental temperatures.Consequently,for both the studied samples BET SSA decreased by~58%and 72%at 350℃,and~67%and 68%at 500℃,whereas average pore diameter increased by~45%and 91%at 350℃,and~100%and 94%at 500℃ compared to their untreated counterparts.CO_(2) adsorption results,unlike N_(2),revealed a pronounced rise in micropore properties(surface area and volume)at 500 and 650℃(~30%-35%and~41%63%,respectively for both samples),contradicting the N_(2) adsorption outcomes.Scanning electron microscope(SEM)images complemented the findings,showing pore structures evolving from microcracks to collapsed pores with increasing thermal treatment.Analysis of the SEM images of both samples revealed a notable increase in average pore width(short axis):by~4 and 10 times at 350℃,~5 and 12 times at 500℃,and~10 and 28 times at 650℃ compared to the untreated samples.Rock-Eval analysis demonstrated the liberation of almost all pyrolyzable kerogen components in the shales heated to 650℃.Additionally,the maximum micropore capacity,identified from CO_(2) gas adsorption analysis,indicated 650℃ as the ideal temperature for in situ conversion and CO_(2) sequestration.Nevertheless,project viability hinges on assessing other relevant aspects of shale gas development such as geomechanical stability and supercritical CO_(2) interactions in addition to thermal treatment.
基金supported by the High-performance Computing Platform of China University of Geosciences,Beijingsupported by the National Natural Science Foundation of China(Grant No.42304087)+1 种基金the National Key R&D Program of China(Grant No.2022YFF0800901)the Fundamental Research Funds for the Central Universities(Grant No.29-2023-202)。
文摘Since the Cenozoic,a series of extensional south-north normal faults and gneiss-granite domes evolved in the southern Tibetan Plateau,the formation mechanism of which is of scientific interest and which has implications for the tectonic dynamics of the plateau.Typical of such features are the Xainza-Dinggye rift and the Mabja gneiss dome,which are located in the Xainza-Xietongmen-Dinggye region in the central Tibetan Plateau.In this study,Magnetotelluric measurements across this region are used to generate a high-resolution 3-D electrical resistivity model of the subsurface and to analyze the cause of the conductive zones.The large-scale conductive zones identified in the middle-lower crust may result from aqueous melt partial melting,whereas the smaller-scale conductive zones in the upper-middle crust may result from saline fluids,possibly with varying minor volumes of melts.Subsequently,based on the electrical resistivity model and combined with the spatiotemporal coupling of the geological,geochemical,and geophysical data,the state and migration features of crustal materials are discussed.The results show that the upwelling of mantle materials along subduction channels and slab-windows related to the tearing of the Indian lithospheric plate contributed to the partial melting of the middle-lower crust in the Lhasa terrane.Furthermore,partial melting of the upper-middle crust in the Tethys-Himalaya terrane resulted from southern extrusion of crustal materials in the Lhasa terrane.These two mechanisms can significantly reduce the effective viscosity.We speculate that the deformation of the brittle upper crust that is controlled by large-scale ductile layers characterized by weak rheology is the main dynamic mechanism of rift evolution.Meanwhile,the metamorphism and anatexis in the upper-middle crust of the Tethys-Himalaya terrane related to the southern extrusion of materials contributed to the evolution of the Mabja gneiss dome.During the middle Miocene,the southern extrusion of crustal materials may have been influenced by the cooling events beneath the Mabja gneiss dome,which can explain why the deep areas beneath the Mabja gneiss dome have middle-high resistivity.In addition,our study region is located in the Mediterranean-Himalayan seismic belt,and mainly includes shallow-focus earthquakes and intermediate-depth earthquakes.In the north,shallow-focus earthquakes are mainly controlled by the accumulation of stress in the brittle layer of the overlying crust related to the ductile layer of the middle and lower crust.In the south,shallow-focus earthquakes(e.g.,Dingri MS6.8 earthquake)mainly occur in the rigid,resistive block,which is surrounded by conductive zones,possibly because fluid migration may be hindered by these resistive blocks.The intermediate-depth earthquakes are mainly controlled by the response in the subsurface area,which is related to the detachment of the Indian lithospheric mantle from the Indian crust.
文摘Fracture network connectivity and aperture （or conductivity） distribution are two crucial features controlling flow behavior of naturally fractured reservoirs. The effect of connectivity on flow properties is well documented. In this paper, however, we focus here on the influence of fracture aperture distribution. We model a two dimensional fractured reservoir in which the matrix is impermeable and the fractures are well connected. The fractures obey a power-law length distribution, as observed in natural fracture networks. For the aperture distribution, since the information from subsurface fracture networks is limited, we test a number of cases： log-normal distributions （from narrow to broad）, power-law distributions （from narrow to broad）, and one case where the aperture is pro- portional to the fracture length. We find that even a well- connected fracture network can behave like a much sparser network when the aperture distribution is broad enough （c~ 〈 2 for power-law aperture distributions and σ ≥ 0.4 for log-normal aperture distributions）. Specifically, most fractures can be eliminated leaving the remaining dominant sub-network with 90% of the permeability of the original fracture network. We determine how broad the aperture distribution must be to approach this behavior and the dependence of the dominant sub-network on the parameters of the aperture distribution. We also explore whether one can identify the dominant sub-network without doing flow calculations.
文摘Wettability alteration of carbonate reservoirs from oil-wet to water-wet is an important method to increase the efficiency of oil recovery. Interaction between surfactants and polymers can enhance the effectiveness of surfactants in EOR applications. In this study, the interaction of polyethylene glycol(PEG) with an ionic surfactant, sodium dodecyl sulphate(SDS),is evaluated on an oil-wet carbonate rock surface by using contact angle measurements. The results reveal that wettability alteration of carbonate rocks is achieved through PEG/SDS interaction on the rock surface above a critical aggregation concentration(CAC). The behaviour of PEG/SDS aqueous solutions is evaluated using surface and interfacial tension measurements. Furthermore, the effect of PEG and SDS concentrations and impact of electrolyte addition on PEG/SDS interaction are investigated. It is shown that electrolyte(NaCl) can effectively decrease the CAC values and accordingly initiate the wettability alteration of rocks. Moreover, in a constant SDS concentration, the addition of NaCl leads to a reduction in the contact angle, which can also be obtained by increasing the aging time, temperature and pre-adsorption of PEG on the rock surface.
基金theSSocial Development Project of Science and Technology Commission of Shanghai Municipality(No.21DZ1201105)the Fundamental Research Funds for the Central Universities(No.21D111320)the National Natural Science Foundation of China(Grant No.42201489).
文摘Quasi-rectangular shield tunneling is a cutting-edge trenchless method for constructing metro tunnels with double tubes,owing to its advantages in saving underground space and reducing ground disturbance.However,the conventional quasi-rectangular shield tunneling method is not applicable when constructing a tunnel without a center pillar,such as a scissor crossover section of a metro line.Therefore,the O-0 tunneling method,which combines the quasirectangular shield and pipe jacking methods,was investigated in this study to solve the aforementioned construction challenges.This study presents a case study of the Sijiqing Station of the Hangzhou Metro Line 9 in China,in which the O-0 method was first proposed and applied.Key techniques such as switching between two types of tunneling modes and the tunneling process control in complex construction environments were investigated.The results demonstrated that the O-0 method can address the technical challenges presented by the post-transition line with a high curvature and a scissors crossover line.In addition,the adoption of the 0-0 method ensured that the transformation between shield tunneling and pipe jacking was safe and efficient.The ground settlement monitoring results demonstrated that the disturbance to the surrounding environment can be limited to a safe level.This case study contributes to the construction technology for a metro tunnel containing both post-transition lines with a small turning radius and a scissors crossover line.A practical construction experience and theoretical guidance were provided in this study,which are of significance for both the industry and academia.
